Switch operating trigger with integral biasing means and excessive force protection means

ABSTRACT

A grass trimmer having an electric motor, a rotary blade, a handle extending from the motor, and a trigger switch in the grip portion of the handle. The trigger switch includes an ON-OFF switch for applying power to the motor and a trigger member. Integral with the trigger member is a resilient extension which abuts a fixed surface in the handle to provide a force biasing the trigger in the off direction to provide an improved &#39;&#39;&#39;&#39;feel&#39;&#39;&#39;&#39; for the operator and providing safer operation by avoiding a hair trigger effect.

United tates Fattent 1 3,646,298 Weber et al. Feb. 29, 11972 [54] SWITCHOPERATING TRIGGER WITH 2,985,740 5/1961 Fisher et al. ..200/157 HNTEGRALBEASING MEANS N 3,549,844 12/1970 Chambers ..200/157 EXCESSHVE FORCEPROTECTION FOREIGN PATENTS OR APPLICATIONS MEANS 1,812,748 8/1969Germany ,200/l57 [72] lnventors: Edwin J. Weber, Baltimore; Roderick 1F.33 237 3/ 953 Germany 200 57 Bunyea, Cockeysville, both of Md.

Primary ExaminerRobcrt A. Schaefer 73 A s Th 1 k d D k M f l S lgnce f gi iz S er acturmg Assistant ExaminerRobert A. Vanderhye iAll0rneyLeonard Bloom, Joseph R. Slotnik and Edward D. [22] Filed: Aug.25, 1970 Murphy [21] Applv No.: 66,830 [57] ABSTRACT A grass trimmerhaving an electric motor, a rotary blade, a 7

handle extending from the motor, and a trigger switch in the [58] Fieid61 85 A 153 v grip portion of the handle. The trigger switch includes anON- 206/153 1 OFF switch for applying power to the motor and a triggermember. Integral with the trigger member is a resilient extension whichabuts a fixed surface in the handle to provide a [56] References cuedforce biasing the trigger in the off direction to provide an im- UNITEDSTATES PATENTS proved feel" for the operator and providing saferoperation by avoiding a hair trigger effect. 3,390,242 6/1968 Koepke..200/153 V 3,594,529 7/1971 Cartwright ..200/l72 A 4 Claims, 4 DrawingFigures Patented Feb. 29, 1972 INVENTORS EDWIN J. WEBER RODERICK F.BUNYEA SWITCH OEERATING TRIGGER WITH INTEGRAL BIASING MEANS ANDEXCESSIVE FORCE PROTECTION MEANS The present invention relates to lowcost electric motordriven devices which include a handle portion adaptedto be grasped by an operator and having a trigger switch for controllingthe operation ofthe motor.

In conventional trigger switches, it is customary to provide a springfor biasing the trigger to the OFF" position. This serves to prevent thetrigger from being loose despite the necessary tolerance between theswitching region in the power control switch and the portion of thetrigger which operates the switch. This spring also provides a reactiveforce against the operators finger throughout the motion of the trigger.This is more satisfactory than a loose arrangement which may create theimpression of sloppiness.

In many cases, the trigger member is permanently coupled to the switchoperating member so that the spring which biases the switch to the OFFposition may also be used to bias the trigger member in this manner.However, in the interest of reducing the cost of the device to theconsumer, it is often desired to use a standard switch, such as a slideswitch and to 7 control it by means of a trigger member which abuts andpushes against the slider button in the ON direction but which has somefree movement when the switch slider is in its OFF position. To take upthis slack, it is necessary to add an independent spring force whichincreases the cost, thus partially defeating the purpose of using theslide switch. It is the purpose of this invention to avoid the necessityfor this extra cost and to provide an improved trigger for use in thisdesign and in others where a biasing force applied directly to thetrigger member may be desirable.

It is accordingly an object of this invention to provide an improvedtrigger switch including a low cost biasing means.

It is also an object to provide an improved trigger member which doesnot require an independent biasing member.

Another object is the provision of an improved, low cost handle andtrigger switch assembly in which the trigger is biased to the normalposition.

Further objects and advantages will become apparent as the descriptionand illustration of this invention proceed.

Briefly, in accord with one embodiment of this invention, a handle andtrigger assembly is provided wherein the trigger is pivotally mountedfor movement within the handle. The trigger includes an exposed memberfor actuation by an operator and a rigid extension thereof for operatinga power switch. In accord with this invention, a resilient extension isprovided-integral with the trigger, which abuts a portion of the handleso as to be flexed when the trigger is moved by the operator. Theresilient member is flexed a small amount even when the trigger is inthe fully released position, thus providing a resistance to any movementof the trigger by the operator. This compensates for any looseness inthe construction and provides the feel" desired by the operator. In thedrawin FIG. I is a perspective view ofa grass trimmer which utilizes thepresent invention;

FIG. 2 is a perspective view ofan improved trigger in accord with thisinvention;

FIG. 3 is a partial cross-sectional view of the handle assembly of thetrimmer of FIG. 1 showing the trigger in the OFF position; and

FIG. 4 is a view similar to FIG. 3 but showing the trigger in the ONposition.

in FiG. l, a grass trimming device is illustrated as an exemplaryapplication of the trigger switch of this invention. The trimmer showncomprises a cutting blade partially enclosed by a guard 11 and driven byan electric motor, not shown, which is enclosed within housing 12. Ahandle 13 extends from the housing and terminates at its upper end in ahandle grip portion I4. A trigger 15 is provided for controlling theapplication of power to the electric motor. For example, the tool may beadapted for connection via an extension cord to an AC outlet or it maybe adapted for battery power. In either case,

movement of the trigger 15 into the handle by the operator is effectiveto cause operation ofthe motor.

FIG. 2 illustrates the trigger of this invention and FIGS. 3 and 4respectively show-the trigger 15 in its outer and inner positions withinthe handle. The trigger 15 comprises a trigger member 16 which ismounted within the handle 14 via a pivot 17. The trigger member I6 isshaped in the usual manner to provide a comfortable surface for theoperator's finger during operation. The pivot 17 is integral with thetrigger member and consists of a pair of round extensions on oppositesides of the trigger which rest in appropriate slots 18 formed in theinternal structure of the handle I4.

The trigger 15 also includes an integral and relatively rigid extension19 which serves as the switch operating member. As can be seen in FIG.4, this extension is arranged to encounter the slide button 20 of aslide switch 21 as the trigger is depressed by the operator and shiftthe slide button. thus changing the connection to terminals 22 from OFFto ON. These terminals are appropriately connected between the powersource and the motor so as to control the operation thereof. Althoughthe member I9 is relatively rigid, it is noted that it may be slightlyflexible upon the application of an unusually large force so as toreduce the possibility of breaking the slide button 20 or the switch 21.This flexing is illustrated in FIG. 4.

In particular accord with this invention, the trigger 15 also includes asecond integral extension 23 which is normally straight as shown in FIG.2 and must be flexed slightly in order to accommodate the trigger withinthe confines of its mounting location with the handle (FIG. 3). Thus theextension 23 serves 'to bias the trigger member 16 outwardly toward theOFF position at all normal positions of the trigger member. Outwardmovement of the trigger is limited by the stops 24, 25. Accordingly,this member compensates for the free movement which would otherwise bepresent due to the space between the end of the operating extension 19and the slide button 20. It is noted that this space is generallydesired to provide some movement of the trigger before actual operationof the switch occurs.

The flexible extension 23 is madejust sufficiently flexible so as toallow the operator to depress the trigger freely and withoutobstruction, but at the-same time to provide enough resistance tomovement for the operator to be aware of this force. This reactive forceis generally preferred by almost all users of trigger operated devices.It will be noted in FIG. 4 that the degree of bending of the extension23 has increased due to the inward movement of the trigger member 16about the pivot 17.

It has been stated above that the trigger member 16, the extensions 19and 23, and the pivot 17 are integrally formed. Preferably, this triggercomprises an injection-molded plastic such as nylon which is formed byproviding an appropriately shaped die and injecting the liquid materialwhich is then cured into the shape illustrated in FIG. 2. In thismanner, either this or similar materials may be formed easily into theprecise shape desired and the biasing means desired in such triggers isautomatically provided without further cost or assembly. It can be seenthat the trigger member 16 is sufficiently thick to provide a relativelyrigid body under any normally expectable finger pressure. The member 19may be approximately O. 15-inch thick and only about l-inch long, thusproviding a resistance to flexing which is sufficient to withstand mostfinger pressures but which will yield before the slide button breaks ifan unusually high force is applied. The extension 23 must be on theorder of 0.085-inch thick and about 1.4-inch long, thus providing alimited biasing force which is easily overcome by an operator's finger.

It will be noted that many modifications from the illustrated embodimentcan be made without departing from the concept of this invention. Forexample, other types of pivoting or linear movement of the trigger maybe accommodated with a basically similar flexible extension whichprovides the described biasing force. It is also noted that a slot couldreadily be formed in an extension of the member 19 to accommodate theslide button 20, in the event that it was desired to make use of theforce of extension 23 to assist in returning the slide button 20 to theoutboard position. As a further modification, the extension 23 itselfcould abut against a special member within the handle or it could belocated at adifferent angular position within the handle, if desired.Such modifications also provide an initial trigger movement against asmall force, thus avoiding the danger of a hair trigger device andincreasing the safety of the unit. Accordingly it is intended in theappended claims to cover all such changes and modifications as may comewithin the true spirit and scope of this invention.

We claim:

1. A handle and trigger assembly for controlling the applica tion ofpower to an electric tool comprising:

mounting locations in said handle for a trigger member and a powerswitch; an opening in the surface'of said handle; a trigger membercomprising a single body of insulating material mounted within saidhandle having a pivot, and including a first member integral with saidpivot extending through said opening for movement between an ON positionand an OFF position by an operator;

at second member integral with said pivot and arranged to operate saidpower switch upon movement of said trigger member between saidpositions, said second member being rigid with said first member undernormal pressure by said operator and being adapted to flex upon theapplication of higher force levels whereby said second member protectssaid power switch against damage; and

a third member integral with said pivot and bearing against a fixedsurface within said handle to provide a biasing force urging saidtrigger member into said OFF" position, said second extension beingflexible under ordinary operator finger pressure.

2. A handle and trigger assembly as claimed in claim I wherein saidsecond member is spaced from said power switch in said OFF" position.

3. A finger-actuatable trigger for controlling a power switch in anelectric tool comprising a single body of insulating material includinga pivot portion adapted to be rotatably mounted within a handle;

a first radial extension from said pivot providing a trigger memberengageable by an operator for movement between an ON" position and anOFF position;

a second radial extension from said pivot arranged to operate a powerswitch upon movement of said trigger member between said positions; and

a third radial extension from said pivot arranged to bear against afixed surface, said third extension being flexible so as to provide abiasing force urging said trigger member into said OFF" position.

4. A trigger as claimed in claim 3 wherein said second radial extensionis more flexible than said trigger member and less flexible than saidthird radial extension.

1. A handle and trigger assembly for controlling the application ofpower to an electric tool comprising: mounting locations in said handlefor a trigger member and a power switch; an opening in the surface ofsaid handle; a trigger member comprising a single body of insulatingmaterial mounted within said handle having a pivot, and including afirst member integral with said pivot extending through said opening formovement between an ''''ON'''' position and an ''''OFF'''' position byan operator; a second member integral with said pivot and arranged tooperate said power switch upon movement of said trigger member betweensaid positions, said second member being rigid with said first memberunder normal pressure by said operator and being adapted to flex uponthe application of higher force levels whereby said second memberprotects said power switch against damage; and a third member integralwith said pivot and bearing against a fixed surface within said handleto provide a biasing force urging said trigger member into said''''OFF'''' position, said second extension being flexible underordinary operator finger pressure.
 2. A handle and trigger assembly asclaimed in claim 1 wherein said second member is spaced from said powerswitch in said ''''OFF'''' position.
 3. A finger-actuatable trigger forcontrolling a power switch in an electric tool comprising a single bodyof insulating material including a pivot portion adapted to be rotatablymounted within a handle; a first radial extension from said pivotproviding a trigger member engageable by an operator for movementbetween an ''''ON'''' position and an ''''OFF'''' position; a secondradial extension from said pivot arranged to operate a power switch uponmovement of said trigger member between said positions; and a thirdradial extension from said pivot arranged to bear against a fixedsurface, said third extension being flexible so as to provide a biasingforce urging said trigger member into said ''''OFF'''' position.
 4. Atrigger as claimed in claim 3 wherein said second radial extension ismore flexible than said trigger member and less flexible than said thirdradial extension.